Conversion of hydrocarbon oils



jam M 1g R. .1.1 DEARBORN Erm.. 2,228,510

CONVERSION OF HYDROCARBON OILS Filed June 1, 1959 40 ation.

Patented Jan. 1.4, 1941 UNITED -STATES Pn'liaN'rf` oFrlcE ooN'vEnsIoN or mmaocARoN oILs Richard J. Dearborn, Summit, N. J., and Le Roy G. Story', White Plains, N. Y., assignors to The Texas Company, New York, N. Y., a corporation of Delaware 'Application June 1, 1939, Seriall No. 276,786 `3 claims.' (ol. iss-tz) 'Ihis invention relates to the conversion of hydrocarbon oils and has lto do particularly with a combination unit involving thermal and catalytic cracking.

In accordance with the invention, a hydrocarbon oil, Whichmay be unsuitable for catalytic cracking due to excess carbon formation, is subjected to thermal cracking, the cracked products separated into a residuum, an intermediate gas l0 oil fraction and gasoline. The intermediate gas oil fraction may be subjected to solvent extraction with a selective solvent, to separate an extract and rainate. The raiiinate is subjected to cataiytic cracking to form gasoline and a recycle stock whichl may be recycled to the thermal cracking operation. The residuum from the thermal cracking operation may be subjected to ilash distillation to form a cycle gas oil which may be charged to the solvent refining operation or recycled to the thermal cracking operation, -or

both. The invention is particularly adapted to a clean circulation operation wherein the Afresh charge may be contacted with the cracked'vapors from the thermal cracking operation to form a mixture of reuxcondensate vand unvaporized charging stock which is charged to the thermal cracking operation land a superclean vrecycle'stock which is. charged to the solvent extraction operation'. The extract from the solvent extractionoperation may advantageously charged to the thermal cracking operation.

According to amodication of the invention,

a hydrocarbon oil which may; be suitable for cat'- alytic cracking, may be subjected to catalytic cracking and a gasoline and a recyclestocksepstead of subjecting the recyclev stock from the catalytic cracking operationr to solvent extraction, this recycle stock may b'e charged directly to the thermal cracking operation, and the recycle stock from the thermal cracking operation subjected to the solvent-extraction to produce a railinate, which is charged tothe catalytic cracking operation, and an extract Whichis returned to the thermal cracking operation.

The invention will be more fully understood from the following description read in connection with the accompanying drawing which shows one form of apparatus for carrying out the process of the invention.

Referring to the drawing, a fresh charge stock such as crude oil, reduced crude or heavy gasoil a receiver 42.

is chargedthrough the line I .by the pump 2'to a fractionator 3. The charge is contacted with cracked .vapors introducedV through line 4, thereby forming a mixture, comprising unvaporized fresh' charge `and reux condensate. 'I'he mixture is collected in the `bottom of fractionator. 3 from whence it is Withdrawn through the line 5 and pump 6, for recycling to the system. The` vapors pass overhead from fractionator 3 through the line l to a secondary fractionator 8.- In'the. latter, fractionation takes place to separate gasoline vapors. Which are passed overhead from the fractionatorI throughthe line 9 and `.condenser I0 to an accumulator I 2 wherein a gasoline distillate is collected.`

A secondaryor superclean condensate 'is collected in the lower portion of the Ziractionator 8 and drawn oi through 'the line I 4. Thesuperclean vcondensate is passed through a cooler I8, pump I9 and line-.20 to a mixer2l. wherein it is intimately contacted with va solvent introduced through line 23 by the pump 2L The solvent is intended to be one which will cause separation of the more paramnic constituents from the-less parailinic' constituents.. The solvents4 contemplated are SO2', furfuraL'nitrobenzene, phenol, and the like. A mixture of solventand oil is transferred from 'the mixer through line l25 to a separator 26 wherein settle out. T-he rainate layer tion of the settler', comprising'largely paraillnic raffinate and extractlayers hydrocarbons, and substantially fr ee from solvent, is drawn from the to'p of the .settler Ithrough, the line 28 by the pump'29 and charged to a heating coil 3l)l located inafurnace 3i. In case it is necessary to make a further separation of Y 30v collecting in theupper porsolvent from the rafllnate, astill may be installed in the line 28 for strippingthe'solvent'from the hydrocarbons. A clean charging stock, suitable for catalytic cracking. such as virgin gas oil, may

be introduced through the line 3 2 bythe pump 33. l In the heating coil the oil isv raised to temperatures sufficiently high for ,purposes of catalyticcracking. This temperature may be about 750? to 950 F. 'Pressures are preferably about atmospheric or slightly above. The hot oil. is transferred from the heating coil through theline 3| to a catalyst chamber 35.v In passing through, l the catalyst chamber the oil is contacted with a;

suitable crackingfcatalyst, such as active alumina',

acid-treated clays, synthetic aluminum silicates,

silica gel and the like. "The cracked productsare transferred from fthe' catalyst chamber. .35 through'the line 33 to fractionator 38. In the fractionator, hydrocarbons Aof gasoline boiling range are separated as vapors and passed overhead through the line 39 and condenser 140 vto A recycle stock of higher boiling range than gasoline is collected in the lower portion of the fractionator 38 and withdrawn through the line 44. This recycle stock may be passed through the line 45 by the pump 45 to the mixer 2i to 5 undergo solvent extraction. The recycle stock may, however, be passed through the line 48, pump 50, line 5l and line 52 tothe heating coil 53 located ina furnace 54. In the coil 55, the oil is subjected to cracking conditions of temperature and pressure, such as about 800-to 1000 F. and 200 to 1000 pounds. The products from the coil 53 are passed through the transfer line 55 together with admixed reflux condensate and unvaporized charging stock from the line 5 to'a soaker or reaction chamber 55." The cracked products are passed from the soaker 58 through line 58 to separator 60 wherein a separation between vapors and unvaporized oil occurs. The vapors are passed overhead through the line 4 to the fractionator 8, referred 'to heretofore.

A residuum or tar is drawn from the bottom of the separator G0 and conducted through line 63 to a tar stripper 54 wherein the tar is flashed by reduction of pressure through valve 85 in the line 63. Fuel oil is drawn from the bottom of the tar stripper through the line 81. Vapors cornprising cycle gas oil are passed overhead through the vapor line' 58 and condenser 10. The condensate is then pumped by the pump 1| through the line 52 back to the heating coil 53. Any portion or all of the oil may be discharged from the system through the line 13, or passed through the line 15 to the mixer 2 I. v The extract layer, comprising naphthenes, aromatics, olefinic hydrocarbons and solvent, collected in the lower portion of the settler 26, is

passed through the line 18 by the pump 18 to a still 80. In the still the solvent is vaporized and passed overhead through the vapor line 8l and A condenser 82. The condensate is then pumped by the pump 84 through the line 85 to the mixer 2l for reuse. The extract portion remaining in the still 80 is drawn off from the bottom thereof through the line 85 and may be discharged from the system or passed through the line 88 by the pump 90 for charging through the line 52 to the heating coil 53 of the thermal cracking system.

As an example of the operation 'of the invention, a. reduced crude is charged to the primary ofractionator of a thermal cracking unit. The resulting mixture of unvaporized charge and heavy reflux condensate, collected as a so-ealled black oil in the lower portion of the fractionator, The unis withdrawn and passed to a soaker. 55 condensed vapors from .the fractionator are passed to a secondary fractionator wherein a gasoline fraction Aand a 'superclean recycle stock are separated. The superclean recycle stock is subjected to' solvent extraction with furfural. The rafiinate is subjected to catalytic cracking at temperatures of about 900 F and about atmospheric pressure, in the presence of asilica-alumina catalyst. The cracked products are fractionated to separate a gasoline fraction and a recycle stock. I'he recycle stock is subjected to thermal cracking at a temperature of about 930 F.' and 400 pounds pressure in a coil and soaking drum. 'I'he cracked products are separated into vapors and residuum, and the vapors discharged into the primary fractionator referred to heretofore. The residuum is ash distilled to produce a fuel oil and a cycle gas oil which is returned to the coil of the thermal cracking system. The solvent and extracted hydrocarbons are subjected to distillation to separate the solvent which is returned to the solvent extraction system. The extract sep- 5 arated from the solvent is charged to the thermal cracking operation. The thermally and catalytically cracked gasolines when blended together show an octane number of about '18 and a yield of about l70%. l0

As another example of the operation of the invention, a virgin gas oil is subjected to catalytic cracking at temperatures of about 930 F and about atmospheric pressure in the presence of an acid treated clay catalyst. The cracked products 15 are separated into a gasoline fraction and a recycle stock. The recycle stock is subjected to thermal cracking at temperatures of about 950 F. and about 300 pounds pressure. The thermally cracked products are separated into residuum, 20 clean recycle stock and a gasoline fraction. The clean recycle stock is subjected to solvent extraction with SO: to produce a rafiinate and an extract. The railinate is charged to the catalytic cracking operation and the extract is returned to 25 the thermal cracking operation. The total gasoline yield is about '15% and shows an octane number of about 80.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be 30 made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim: 3 1. A process for the conversion of hydrocarbon oils which comprises subjecting the oilto thermal cracking wherein high boiling oils are converted into gasoline by heat and pressure, separating the cracked products into gasoline, resid- 40 uum and a clean gas oil recycle stock, subjecting said residuum to flash distillation to separate a cycle gas oil, subjecting said cycle gas oil and said clean gas oil recycle stock to solvent extraction to separate a raffinate and an extract fraction, 45 subjecting said rafiinate fraction to catalytic cracking, separating from the reaction products of the catalytic cracking operation gasoline and a recycle stock, and passing said recycle stock to the thermal cracking operation. 50

A 2. A process for the conversion of hydrocarbon oils which comprises contacting fresh charging stock with cracked vapors from a thermal cracking operation thereby forming a mixture of unvaporized fresh charge and reux condensate, re- 55 cycling said mixture to said thermal cracking 'operation. -further fractionating the vapors to form a reflux condensate, subjecting said reflux condensate to solvent extraction to separate a raml nate and an extract portion, charging the rafli- 60 nate portion to' a catalytic cracking operation, recovering from the catalytic cracking operation gasoline and a recycle stock and passing said last v mentioned recycle stock to said thermal cracking operation. 65 3. A process according to claim 2 in which said extract portion is returned to the thermal cracking operation.

I RICHARD J. DEARBORN.

LE ROY 'G. STORY. 70 

